Transient nanobubbles in short-time electrolysis

Abstract

Water electrolysis in a microsystem is observed and analyzed on a short-time scale ~10 us. Very unusual properties of the process are stressed. An extremely high current density is observed because the process is not limited by the diffusion of electroactive species. The high current is accompanied by a high relative supersaturation S>1000 that results in homogeneous nucleation of bubbles. On the short-time scale only nanobubbles can be formed. These nanobubbles densely cover the electrodes and aggregate at a later time to microbubbles. The effect is significantly intensified with a small increase of temperature. Application of alternating polarity voltage pulses produces bubbles containing a mixture of hydrogen and oxygen. Spontaneous reaction between gases is observed for stoichiometric bubbles with the size smallaer than 150 nm. Such bubbles disintegrate violently affecting the surface of electrodes.